GlaxoSmithKline declines option on Ionis' experimental TTR amyloidosis therapy inotersen

GlaxoSmithKline decided against taking an option on Ionis Pharmaceuticals' experimental antisense drug inotersen designed to treat patients with transthyretin (TTR) amyloidosis, Ionis said Friday. According to Ionis, GlaxoSmithKline made the decision "as part of a reprioritisation of its pipeline and strategic review of its rare diseases business."

The news comes after Ionis announced in May that the Phase III NEURO-TTR study of inotersen in patients with polyneuropathy due to hereditary TTR amyloidosis met both its main goals. However, questions have been raised about the safety profile of the therapy, with Ionis noting that in the NEURO-TTR trial there were three serious cases of thrombocytopaenia, including one death from intracranial haemorrhage (for related analysis, see ViewPoints: Efficacy data for Ionis' inotersen leaves GlaxoSmithKline with a tough decision).

Commenting on the latest news, Leerink analyst Paul Matteis said GlaxoSmithKline's decision to return rights to inotersen was not a major surprise given its shifting pharmaceutical focus, but noted that it creates new problems for Ionis. The analyst added that the move "may increase investor scrutiny" on inotersen's safety profile, while Ionis could be "behind the curve with respect to launch preparedness."

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Ionis noted that it will regain all rights to inotersen, which is expected to be submitted to regulators this year, ahead of a possible launch in 2018. The company's chief operating officer Lynne Parshall remarked "we are prepared to independently advance inotersen and remain on track to file for marketing approval of inotersen in the US and EU this year." According to Ionis, GlaxoSmithKline also decided against exercising its option on IONIS-FB-LRx, a ligand conjugated antisense drug under development for the treatment of complement-mediated diseases.

GlaxoSmithKline initially gained rights to inotersen as part of a 2010 partnership with Ionis, previously named Isis Therapeutics, focused on RNA therapeutics. Ionis said Friday that it may form a subsidiary to help sell inotersen in North America, and is also in discussions with new partners.

Meanwhile, Alnylam Pharmaceuticals is also developing the RNA-based treatment patisiran for the treatment of familial amyloid polyneuropathy, with key Phase III data expected to be unveiled next month. For additional analysis, read ViewPoints: Ionis builds case for inotersen, but all eyes remain fixed on APOLLO.

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